The aim of this proposal is to create a Standardization Program for Bone Lead measurements (BLSP) obtained via reference methods and via in vivo X-Ray Fluorescence (XRF). The BLSP will fulfill current needs of the bone lead methodologies: lack of appropriate certified reference materials (RMs) and lack of traceability. The BLSP will also provide RMs for electrothermal atomic absorption spectrometry (AAS) and inductively coupled plasma-mass spectrometry (ICP-MS) and will conduct an interlaboratory validation study among laboratories using those methods. The program will also provide RMs for XRF, thereby providing traceability to SI units, and will conduct an interlaboratory validation study among laboratories using XRF for in vivo bone lead measurements. There are six goals: first to cross-validate AAS and ICP-MS in the Wadsworth Trace Elements Laboratory of the New York State Department of Health (NYS DOH); second to establish a national repository of RMs for bone lead measurement via AAS and ICP-MS traceable to NIST SRM 1486 Bone Meal and 1400 Bone Ash; third, to conduct an interlaboratory validation of AAS and/or ICP-MS for bone lead measurement. The fourth goal is to assemble a national repository of RMs for bone lead XRF by preparing two sets of well-characterized goat bone samples containing endogenous lead concentrations that encompass those found in human populations; the fifth goal is to conduct an in vitro XRF interlaboratory validation and comparison study using the two sets of goat bone samples. The first set of XRF RMs will be destroyed as part of the process of obtaining reference concentrations via AAS and ICP-MS for both surface and core bone that are traceable to SI units. The reference concentrations thus obtained will form the basis of the assessment of XRF accuracy. The second set of XRF RMs will be created and used for a second interlaboratory comparison and will be preserved for long-term use. The sixth and last goal is to conduct an in vivo XRF validation study using the euthanized members of the NYS DOH goat colony that will provide the RMs. XRF-measured in vivo concentrations will be compared to the reference concentrations obtained from AAS and ICP-MS. [unreadable] [unreadable]